A shape memory alloy (hereinafter, may be referred to as SMA) has a characteristic that, even if it is applied with external force at the martensite transformation starting temperature or lower and is deformed plastically, if it is heated up to the reverse transformation ending temperature or higher, it is restored to the memorized shape. An art for using an SMA having such a characteristic as an actuator is known.
When performing image stabilization by an actuator using an SMA (hereinafter, may be referred to as SMA actuator), a driving performance of canceling image shaking of at least about 10 Hz is required.
Therefore, an art for improving the driving performance of the SMA actuator having a low response, for example, is proposed in Patent Document 1. The art performs a differential operation two times or more in a servo control system to improve a phase lag, thereby enhances the response of the SMA actuator.
Patent Document 1: Japanese Laid-Open Patent Application 2003-125590
However, the art of Patent Document 1 aforementioned performs the differential operation two times or more, so that noise included in a measurement signal such as position is amplified, thus a special filter is necessary for a countermeasure therefore. Further, there is a problem imposed that tuning of the aforementioned differential control is difficult and corrections according to changes in the environmental temperature are necessary. As mentioned above, when improving the response of the SMA actuator only by improvement of the control system (software), various problems are caused as side effects, thus the response cannot be improved appropriately.